The figure below shows the forces acting on a child who is balancing on a pogo stick.

Transcription

1 The figure below shows the forces acting on a child who is balancing on a pogo stick. The child and pogo stick are not moving. (a) The downward force of the child on the spring is equal to the upward force of the spring on the child. This is an example of which one of Newton s Laws of motion? Tick one box. First Law Second Law Third Law () (b) Complete the sentence. Use an answer from the box. elastic potential gravitational potential kinetic The compressed spring stores... energy. () Page of 60

2 (c) The child has a weight of 343 N. Gravitational field strength = 9.8 N / kg Write down the equation which links gravitational field strength, mass and weight. () (d) Calculate the mass of the child. Mass =... kg (3) (e) The weight of the child causes the spring to compress elastically from a length of 30cm to a new length of 23cm. Write down the equation which links compression, force and spring constant. () (f) Calculate the spring constant of the spring. Give your answer in newtons per metre. Spring constant =... N / m (4) (Total marks) 2 On 4 October 202, a skydiver set a world record for the highest free fall from an aircraft. After falling from the aircraft, he reached a maximum steady velocity of 373 m / s after 632 seconds. (a) Draw a ring around the correct answer to complete the sentence. This maximum steady velocity is called the frictional initial terminal velocity. () Page 2 of 60

3 (b) The skydiver wore a chest pack containing monitoring and tracking equipment. The weight of the chest pack was 54 N. The gravitational field strength is 0 N / kg. Calculate the mass of the chest pack... Mass of chest pack =... kg (2) (c) During his fall, the skydiver s acceleration was not uniform. Immediately after leaving the aircraft, the skydiver s acceleration was 0 m / s 2. (i) Without any calculation, estimate his acceleration a few seconds after leaving the aircraft. Explain your value of acceleration in terms of forces. Estimate... Explanation... (3) Page 3 of 60

4 (ii) Without any calculation, estimate his acceleration 632 seconds after leaving the aircraft. Explain your value of acceleration in terms of forces. Estimate... Explanation... (3) (Total 9 marks) 3 A student carries out an investigation using a metre rule as a pendulum. (a) Diagram shows a metre rule. Diagram (i) (ii) Draw, on Diagram, an X to show the position of the centre of mass of the rule. State what is meant by the centre of mass of an object. () () Page 4 of 60

5 (b) The student taped a 00 g mass to a metre rule. She set up the apparatus as shown in Diagram 2. She suspended the metre rule from a nail through a hole close to one end, so she could use the metre rule as a pendulum. The distance d is the distance between the nail and the 00 g mass. Diagram 2 (i) Draw, on Diagram 2, a Y to show a possible position of the centre of mass of the pendulum. () Page 5 of 60

6 (ii) The student carried out an investigation to find out how the time period of the pendulum varies with d. Some of her results are shown in the table. Time for 0 swings in seconds d in cm First test Second test Third test Mean value Mean time for swing in seconds Complete the table. You may use the space below to show your working. (3) Page 6 of 60

7 (iii) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. Describe how the student would carry out the investigation to get the results in the table in part (ii). You should include: any other apparatus required how she should use the apparatus how she could make it a fair test a risk assessment how she could make her results as accurate as possible. (6) Page 7 of 60

8 (c) A graph of the student s results is shown below. Distance d in cm (i) Describe the pattern shown by the graph. (2) Page 8 of 60

9 (ii) The student thinks that the measurements of time for d = 0 cm might be anomalous, so she takes a fourth measurement. Her four measurements are shown below. 5.3 s 5.4 s 5.5 s 5.3 s State whether you consider any of these measurements to be anomalous. Justify your answer. (2) (Total 6 marks) 4 The diagram shows the passenger train on part of a rollercoaster ride. (a) Which arrow shows the direction of the resultant force acting on the passenger train? Put a tick ( ) in the box next to your choice. () (b) For part of the ride, the maximum gravitational field strength acting on the passengers seems 3 times bigger than normal. Normal gravitational field strength = 0 N/kg (i) Calculate the maximum gravitational field strength that seems to act on the passengers during the ride Maximum gravitational field strength =... N/kg () Page 9 of 60

10 (ii) One of the passengers has a mass of 75 kg. Calculate the maximum weight this passenger seems to have during the ride. Show clearly how you work out your answer Maximum weight =... N (2) (Total 4 marks) 5 (a) The diagram shows the forces acting on a parachutist in free fall. The parachutist has a mass of 75 kg. Calculate the weight of the parachutist. gravitational field strength = 0 N/kg Show clearly how you work out your answer and give the unit. Weight =... (3) Page 0 of 60

11 (b) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. The graph shows how the vertical velocity of a parachutist changes from the moment the parachutist jumps from the aircraft until landing on the ground. Using the idea of forces, explain why the parachutist reaches a terminal velocity and why opening the parachute reduces the terminal velocity. (6) Page of 60

12 (c) A student wrote the following hypothesis. The larger the area of a parachute, the slower a parachutist falls. To test this hypothesis the student made three model parachutes, A, B and C, from one large plastic bag. The student dropped each parachute from the same height and timed how long each parachute took to fall to the ground. (i) The height that the student dropped the parachute from was a control variable. Name one other control variable in this experiment.... () (ii) Use the student s hypothesis to predict which parachute, A, B or C, will hit the ground first. Write your answer in the box. Give a reason for your answer (2) (Total 2 marks) Page 2 of 60

13 6 A student was asked to find the centre of mass of a thin sheet of card. The diagram shows the result of the student s experiment. The student drew two lines onto the card. The centre of mass is where the two lines cross. (a) Describe how the student found the correct positions to draw the two lines. You may include a labelled diagram in your answer. (3) Page 3 of 60

14 (b) Explain how the student can check that the position found for the centre of mass is accurate. (2) (Total 5 marks) 7 The drawing shows a plastic toy which can stand on its feet. (a) (i) Draw an X on the diagram so that the centre of the X marks the likely position of the centre of mass of the toy. Photograph supplied by Hemera/Thinkstock () (ii) Explain the reason for your choice in part (a)(i) () Page 4 of 60

15 (b) Suggest two ways in which the design of the toy could be altered to make the toy more stable (2) (Total 4 marks) 8 The diagram shows a fork-lift truck with a load of 2.4 kn. The clockwise moment caused by this load is 2880 Nm. (a) Use the equation in the box to calculate the distance d. moment = force perpendicular distance from the line of action of the force to the axis of rotation Show clearly how you work out the answer and give the unit. Distance d =... (3) Page 5 of 60

16 (b) This warning notice is in the driver s cab. Explain in terms of moments why the maximum load must not be exceeded. (2) (Total 5 marks) Page 6 of 60

17 9 The diagram shows a back view of a computer monitor. (a) In normal use, the monitor is stable. (i) Explain the meaning, in the above sentence, of the word stable (2) (ii) State the relationship between the total clockwise moment and the total anticlockwise moment about any axis of the monitor when it is stable () Page 7 of 60

18 (b) The instruction booklet explains that the screen can be tilted. It also includes a warning. Caution The monitor can tip over if the screen is tilted too far back. Explain why the monitor will tip over if the screen is tilted too far back. Include the words centre of mass, weight and moment in your explanation. (3) (Total 6 marks) Page 8 of 60

19 0 Two children visit a playground. (a) The diagram shows them on a see-saw. The see-saw is balanced. Complete the following sentences by drawing a ring around the correct word or line in the box. force. (i) The turning effect of the girl s weight is called her load. moment. () balance (ii) Point P is the axis of rotation of the see-saw. turning () the boy moves nearer to point P. (iii) To make end A of the see-saw go up, the girl moves nearer to point P. the girl moves nearer to end A. () Page 9 of 60

20 (b) In another part of the playground, a tyre has been suspended from a bar. (i) Draw an X on the diagram so that the centre of the X marks the centre of mass of the tyre. () (ii) Complete the sentence by using the correct word or phrase from the box. above below to the left of to the right of If the suspended tyre is pushed, it will come to rest with its centre of mass directly... the point of suspension. () (Total 5 marks) Page 20 of 60

21 The diagrams show two concrete mixers. Concrete mixer A Concrete mixer B On each diagram, the centre of the white X marks the centre of mass of the concrete mixer and its contents. (a) Complete the sentence to explain what the term centre of mass means. The centre of mass of a concrete mixer and its contents is... () (b) Both diagrams are drawn to the same scale. Concrete mixer B is more stable than concrete mixer A. The two features which make concrete mixer B more stable are: (2) Page 2 of 60

22 (c) Use the terms line of action of the weight and resultant moment to explain why a stable concrete mixer does not fall over when it is given a small push. (2) (Total 5 marks) 2 The diagram shows the passenger train on part of a rollercoaster ride. (a) Which arrow shows the direction of the resultant force acting on the passenger train? Put a tick ( ) in the box next to your choice. () (b) At the bottom of the slope, the passengers in the train all have the same speed but they each have a different kinetic energy. Why is the kinetic energy of each passenger different? () Page 22 of 60

23 (c) For part of the ride, the maximum gravitational field strength acting on the passengers seems 3 times bigger than normal. Normal gravitational field strength = 9.8 N/kg (i) Calculate the maximum gravitational field strength that seems to act on the passengers during the ride Maximum gravitational field strength =... N/kg () (ii) One of the passengers has a mass of 80 kg. Calculate the maximum weight this passenger seems to have during the ride. Show clearly how you work out your answer Maximum weight =... N (2) (Total 5 marks) 3 The diagram shows a small mobile crane. It is used on a building site. Page 23 of 60

24 The distance, d, is measured to the front of the cab. The table shows information from the crane driver s handbook. Load in kilonewtons (kn) Maximum safe distance, d, in metres (m) (a) What is the relationship between the load and the maximum safe distance? (2) (b) The crane driver studies the handbook and comes to the conclusion that a load of 30 kn would be safe at a distance, d, of 2.0 metres. Is the driver correct? Explain your answer. (2) (c) What is the danger if the driver does not follow the safety instructions? () Page 24 of 60

25 (d) How should the data in the table have been obtained? Put a tick ( ) in the box next to your answer. average results from an opinion poll of mobile crane drivers copied from a handbook for a similar crane results of experiments on a model mobile crane results of experiments on this mobile crane () (Total 6 marks) 4 (a) The diagram shows a child s mobile. The mobile hangs from point P on the ceiling of the child s bedroom. (i) Mark the position of the centre of mass of the mobile by drawing a letter X on the diagram. Do this so that the centre of the X marks the centre of mass of the mobile. () Page 25 of 60

26 (ii) Explain why you have chosen this position for your letter X (2) (b) The diagram shows a device which helps to prevent a ladder from falling over. Use the term centre of mass to explain why the ladder, in the situation shown, is unlikely to topple over. You may add to the diagram to illustrate your explanation. (3) (Total 6 marks) Page 26 of 60

27 5 (a) The diagram shows a rectangle made out of a sheet of cardboard. Draw an X on the diagram so that the centre of the X is at the centre of mass of the rectangle. () (b) The drawing shows a car tyre. (i) Where is the centre of mass of the tyre?... () (ii) Explain your answer to (b)(i) () (Total 3 marks) Page 27 of 60

28 6 Tractors are often used on sloping fields, so stability is important in their design. On the diagram, the centre of the X marks the centre of mass of the tractor. (a) Explain why the tractor has not toppled over. You may add to the diagram to help you to explain. (3) (b) Give two features of the tractor which affect its stability and state how each feature could be changed to increase the tractor s stability. Feature... Feature 2... (2) (Total 5 marks) Page 28 of 60

29 7 The diagram shows the forces on a small, radio-controlled, flying toy. (a) (i) The mass of the toy is 0.06 kg. Gravitational field strength = 0 N/kg Calculate the weight of the toy. Show clearly how you work out your answer and give the unit Weight =... (3) (ii) Complete the following sentence by drawing a ring around the correct line in the box. When the toy is hovering stationary in mid-air, the lift force is bigger than the same as the weight of the toy. smaller than () (b) When the motor inside the toy is switched off, the toy starts to accelerate downwards. (i) What does the word accelerate mean?... () (ii) What is the direction of the resultant force on the falling toy?... () Page 29 of 60

30 (Total 6 marks) 8 (a) The diagram shows a lampshade hanging from the ceiling. Draw an X on the diagram so that the centre of the X marks the centre of the mass of the lampshade. () (a) Complete the sentence using the correct word or phrase from the box. above below to the left of to the right of A suspended object will come to rest with its centre of mass directly... the point of suspension. () Page 30 of 60

31 (c) The diagrams show equipment that a student uses to find the centre of mass of a thin sheet of card. Arrange these sentences in the correct order to describe how the student can find the centre of mass of the card. The sequence starts with sentence D and finishes with sentence E. A B C D E F A line is drawn on the card marking the position of the string. The pin is put through one of the holes in the card and held in the boss. This is repeated using the other hole. Two holes are made in the card with each hole near to the edge of the card. The centre of mass is where the lines cross on the card. The weight is tied to the string and then the string is hung from the pin. D E (3) (Total 5 marks) Page 3 of 60

32 9 (a) Every object has a centre of mass. What is meant by the centre of mass? () (b) The drawing shows a thin sheet of plastic. The sheet is 250 mm wide. Two holes, each with a radius of 2 mm, have been drilled through the sheet. Describe how you could use: a clamp and stand a steel rod 00 mm long and with a radius of I mm a weight on a thin piece of string (= a plumb line) a ruler a pen which will write on the plastic sheet to find the centre of mass of the plastic sheet. To gain full marks in this question you should write your ideas in good English. Put them into a sensible order and use the correct scientific words. (5) Page 32 of 60

33 (c) There is a trapdoor in the ceiling of a house. The trapdoor weighs 44 N. The drawing shows a side view of the trapdoor. (i) Complete the three spaces to give the equation which is used to calculate the turning effect of a force.... =... perpendicular between... line of action and pivot () (ii) Calculate the turning effect, about the hinge, due to the weight of the trapdoor. Show clearly how you work out your final answer and give the unit Turning effect =... (3) (Total 0 marks) 20 (a) The diagram shows a lifebelt. It is hanging freely from hook Y. (i) On the diagram, mark with an X the point where you think the centre of mass of the lifebelt will be. () Page 33 of 60

34 (ii) Explain why you have chosen this point (2) (b) The drawing shows Susan on a diving board. She is.5 metres from point P and she weighs 500 N. Calculate her moment (turning effect) about point P. Show clearly how you work out your answer and give the unit. Moment about P =... (3) (c) Susan has a case with wheels. Page 34 of 60

35 When she packs this case, she puts the heaviest items at the end where the wheels are. This means that the heaviest items are less likely to crush the other contents and it helps her to find things when she opens the case. Explain another advantage of packing her case in this way. To gain full marks in this question you should write your ideas in good English. Put them into a sensible order and use the correct scientific words. (4) (Total 0 marks) 2 (a) The diagram shows three similar toys. Each toy should be able to balance on a narrow rod. The arrows show the direction in which the weight of the toy acts. Page 35 of 60

36 Only one of the toys balances on the rod, the other two fall over. Which one of the toys is balanced? Explain the reason for your choice. (3) (b) The diagram shows a simple toy. Different animal shapes can be positioned so that the 50 cm rod balances horizontally. (i) Calculate the moment exerted by the elephant shape of weight 2N about the pivot P. Show clearly how you work out your answer and give the unit Moment =... (3) Page 36 of 60

37 (ii) Use the following relationship to calculate the weight of the monkey shape. total clockwise moment = total anticlockwise moment Weight =... N (2) (c) The graph shows how the length of the spring changes as the total weight of the different animal shapes change. Use the graph to find how much the spring extends when the elephant shape and the monkey shape are hung from the rod. Show how you get your answer. Extension of spring =... cm (2) (Total 0 marks) Page 37 of 60

38 22 A child stands a wooden brick on its end as shown in the diagram. The child then pushes the brick to make it tilt. How far must the brick be tilted to make it fall over? Explain your answer. (You may draw a labelled diagram if you wish.) (Total 2 marks) 23 Choose words from this list to complete the sentences below. balanced electricity gravity joules magnetism newtons When you drop something it falls. Page 38 of 60

39 This is because it is pulled to the Earth by... We measure forces in units called... When a falling object reaches the ground, it stops moving. This means that the forces acting on it are now... (Total 3 marks) 24 A sky-diver steps out of an aeroplane. After 0 seconds she is falling at a steady speed of 50m/s. She then opens her parachute. After another 5 seconds she is once again falling at a steady speed. This speed is now only 0m/s. (a) Calculate the sky-diver s average acceleration during the time from when she opens her parachute until she reaches her slower steady speed. (Show your working.) (3) (b) Explain, as fully as you can: (i) why the sky-diver eventually reaches a steady speed (with or without her parachute) (3) Page 39 of 60

40 (ii) why the sky-diver s steady speed is lower when her parachute is open.... () (c) The sky diver and her equipment have a total mass of 75kg. Calculate the gravitational force acting on this mass. (Show your working.) Answer... N () (Total 8 marks) 25 The diagram shows two buses. Bus A is empty. Bus B contains bags of sand upstairs to represent passengers. Each bus has been tilted as far as it can without falling over. (a) Each bus will topple over if it is tilted any further. Explain, in as much detail as you can, why this will happen. (You can draw on one of the diagrams as part of your answer if you want to.) (2) Page 40 of 60

41 (b) What difference does it make to the stability of the bus when the upper deck is full of passengers? Explain your answer as fully as you can. (3) (c) Why are the bags of sand in bus B only put upstairs? () (Total 6 marks) Page 4 of 60

42 Mark schemes (a) Third Law (b) elastic potential (c) weight = mass gravitational field strength accept gravity for gravitational field strength accept W = mg accept correct rearrangement ie mass = weight / gravitational field strength or m = W / g (d) 343 = m 9.8 m = m = 35 allow 35 with no working shown for 3 marks (e) force = spring constant compression accept force = spring constant extension accept F = k e accept correct rearrangement ie constant = force / extension or k = F / e (f) compression = 0.07m 343 = k 0.07 k = k = 4900 allow 4900 with no working shown for 4 marks allow 49 with no working shown for 3 marks [] 2 (a) terminal Page 42 of 60

43 (b) 5.4 (kg) correct substitution of 54 = m 0 gains mark 2 (c) (i) 0< a <0 some upward force accept some drag / air resistance reduced resultant force (ii) 0 upward force = weight (gravity) resultant force zero [9] 3 (a) (i) X placed at 50 cm mark (ii) point at which mass of object may be (thought to be) concentrated (b) (i) Y placed between the centre of the rule and the upper part of mass (ii) allow for mark ( ) / 3 value consistent with mean value given only penalise significant figures once 2 Page 43 of 60

44 (iii) Marks awarded for this answer will be determined by the quality of communication as well as the standard of the scientific response. Examiners should apply a best-fit approach to the marking. 0 marks No relevant content Level ( 2 marks) A description of a method which would provide results which may not be valid Level 2 (3 4 marks) A clear description of a method enabling some valid results to be obtained. A safety factor is mentioned Level 3 (5 6 marks) A clear and detailed description of experiment. A safety factor is mentioned. Uncertainty is mentioned examples of the physics points made in the response: additional apparatus stopwatch use of apparatus measure from hole to centre of the mass pull rule to one side, release time for 0 swings and repeat divide mean by 0 change position of mass and repeat fair test keep other factors constant time to same point on swing risk assessment injury from sharp nail stand topple over rule hit someone accuracy take more than 4 values of d estimate position of centre of slotted mass small amplitudes discard anomalous results use of fiducial marker (c) (i) initial reduction in T (reaching minimum value) as d increases 6 Page 44 of 60

45 after 30 cm T increases for higher value of d (ii) (no) any two from: fourth reading is close to mean range of data 0.2 s / very small variation in data is expected 2 [6] 4 (a) correct box ticked (b) (i) 30 ignore added units (ii) 2250 or their (b)(i) 75 correctly calculated allow mark for correct substitution ie or their (b)(i) 75 provided no subsequent step shown an answer of 750 gains mark only if answer to (b)(i) is 0 2 [4] 5 (a) 750 allow mark for correct substitution, ie 75 0 provided no subsequent step shown 2 newton(s) / N do not accept n Page 45 of 60

46 (b) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should also refer to the Marking Guidance, and apply a best-fit approach to the marking. 0 marks No relevant content. Level (-2 marks) There is a brief attempt to explain why the velocity / speed of the parachutist changes. or the effect of opening the parachute on velocity/speed is given. Level 2 (3-4 marks) The change in velocity / speed is clearly explained in terms of force(s) or a reasoned argument for the open parachute producing a lower speed. Level 3 (5-6 marks) There is a clear and detailed explanation as to why the parachutist reaches terminal velocity and a reasoned argument for the open parachute producing a lower speed examples of the physics points made in the response to explain first terminal velocity on leaving the plane the only force acting is weight (downwards) accept gravity for weight throughout as parachutist falls air resistance acts (upwards) accept drag / friction for air resistance weight greater than air resistance or resultant force downwards (resultant force downwards) so parachutist accelerates as velocity / speed increases so does air resistance terminal velocity reached when air resistance = weight accept terminal velocity reached when forces are balanced to explain second lower terminal velocity opening parachute increases surface area opening parachute increases air resistance air resistance is greater than weight Page 46 of 60

47 resultant force acts upwards / opposite direction to motion parachutist decelerates / slows down the lower velocity means a reduced air resistance air resistance and weight become equal but at a lower (terminal) velocity 6 (c) (i) any one from: mass of the (modelling) clay accept size/shape of clay size/amount/volume/shape of clay accept plasticine for (modelling)clay material parachute made from accept same (plastic) bag number / length of strings (ii) C reason only scores if C is chosen smallest (area) so falls fastest (so taking least time) accept quickest/quicker for fastest if A is chosen with the reason given as the largest area so falls slowest this gains mark [2] 6 Resource currently unavailable Page 47 of 60

48 7 (a) (i) centre of X above the feet and in the body a vertical line from their X falls between two lines in diagram - judged by eye (ii) where the mass seems to be concentrated accept it s above the base (area) accept because otherwise it would topple accept line of action (of weight) passes through the base do not accept where the mass is concentrated (b) any two from: make (the area of) feet / base bigger make feet wider apart makes legs shorter / heavier make head smaller / lighter make tail touch the ground / make the tail longer accept make centre of mass / gravity lower 2 [4] 8 (a).2 metre(s)/m allow mark for conversion of 2.4 kn to 2400 N or for correct transformation without conversion ie d = Page 48 of 60

49 (b) any two from: as the load increases the (total) clockwise moment increases danger is that the fork lift truck / the load will topple / tip forward (this will happen) when the total clockwise moment is equal to (or greater than) the anticlockwise moment accept moments will not be balanced (load above 0.0 kn) moves line of action (from C of M) outside base (area) 2 [5] 9 (a) (i) will not fall over () accept will not easily fall over (2) or centre of mass will remain above the base () (line of action of the) weight will remain above within the base accept centre of gravity / c of g / c of m / c m (ii) if the monitor is given a small push () depends on mark above (total) clockwise moment = (total) anticlockwise moment or they are equal / balanced 2 (b) the position of the centre of mass has changed () the line of action of the weight is outside the base () producing a (resultant) moment () points may be expressed in any order 3 [6] 0 (a) (i) moment (ii) (iii) rotation the girl moves nearer to point P Page 49 of 60

50 (b) (i) X drawn in the centre of the space enclosed by the tyre judge by eye (ii) below [5] (a) the point at which the (total) mass seems to act / appears to be concentrated accept weight for mass accept the point at which gravity seems to act do not accept a definitive statement eg where (all) the mass is (b) wider / larger base marks are for a correct comparison lower centre of mass accept lower centre of gravity / c of g (c) line of action (of the weight) lies / falls inside the base in each case the underlined term must be used correctly to gain the mark the resultant moment returns mixer to its original position accept there is no resultant moment / resultant moment is zero accept resulting moment for resultant moment do not accept converse argument [5] 2 (a) correct box ticked Page 50 of 60

51 (b) each passenger has a different mass accept weight for mass ignore other irrelevant factors about the person e.g. mass and height do not accept a list with incorrect factors e.g. mass and position accept passengers started with different (gravitational) potential energy (c) (i) 29.4 (ii) 2400 ignore added units accept their (c)(i) 80 correctly calculated for both marks allow mark for correct substitution of their (c)(i) and 80 an answer of 800 gains mark only if answer to (c)(i) is not 0 2 [5] 3 (a) any two from: inversely proportional as the load gets biggerthe (maximum safe) distance gets less allow as the mass increases the distance decreases accept an unspecified response e.g. big load at a short distance for () load distance = 60 (knm) (b) yes, because 30 2 = 60 (2) accept for () a correct but insufficiently explained response e.g. yes because it s safe accept for (2) a correct response which is sufficiently explained e.g. yes, because 60 (knm) at metre is safe and 30 (knm) is half the load at twice the distance do not accept no and do not accept just yes do not accept yes, because 30 is between 24 and 40 and 2 is between 2.5 and.5 do not accept the crane/ cable may break or other dangers 2 2 Page 5 of 60

52 (c) (d) the crane may/will topple over/fall over/forward results of experiments on this mobile crane accept any unambiguous indication [6] 4 (a) (i) centre of X directly below P and between the model aeroplanes as judged by eye but between centre of propeller of top aeroplane and canopy of bottom aeroplane example (ii) the centre of mass is (vertically) below the point of suspension / P the centre of mass is in the middle of the aeroplanes accept the centre of mass is level with the aeroplanes Page 52 of 60

53 (b) centre of mass of the worker and the ladder (and device) line of action of the weight is inside the base accept the centre of mass is above / within / inside the base (of the ladder and device) so there will not be a (resultant) moment accept so he / it / the ladder will not topple even if he leans over or it will (only) topple over if the line of action of the weight / the centre of mass is outside the base accept each point, either on the diagram or in the written explanation, but do not accept the point if there is any contradiction between them [6] 5 (a) centre of X at the point where the axes cross to within mm in any direction (b) (i) (at / in the) centre (of the tyre) or unambiguously shown on the diagram (ii) (this is) where axes of symmetry (of the tyre) cross / intersect / meet or point at which the mass of the tyre seems to be (concentrated) [3] 6 (a) (line of action of) its weight falls inside its wheel base accept falls between the wheels the first two points may be credited by adding a vertical line from the centre of the X on the diagram () and labelling it weight / force / with a downwards arrow () provided there is no contradiction between what is added to the diagram and anything which may be written (so there is) no (resultant / clockwise) moment / turning effect Page 53 of 60

54 (b) centre of mass should be lower accept centre of gravity accept weight / mass low down not just lower the roof wheel base should be wider accept long axle(s) for wide wheel base allow bigger / larger wheel base do not credit long wheel base responses in either order [5] 7 (a) (i) 0.6 allow mark for correct substitution 2 (ii) newtons accept N do not accept n accept Newtons the same as (b) (i) changed velocity accept increased/ decreased for change accept speed for velocity accept change direction accept getting faster/ slower accept start/ stop moving accept correct equation in terms of change in speed or change in velocity (ii) down(wards) accept towards the ground accept do not accept south [6] Page 54 of 60

55 8 (a) centre of X should appear to be on the continued line of the flex and in the body of the lamp as judged by eye example (b) (c) below (D) B F A C (E) all four correct for 3 marks or any two correct for 2 marks or just one correct for mark 3 [5] 9 (a) point at which its mass (seems to) act or point at which gravity (seems to) act accept... its weight acts accept correct statements if the intent is clear e.g.... if suspended, the centre of gravity will be directly under the point of suspension e.g... (if the object is symmetrical), the centre of gravity is on the or an axis (of symmetry) do not credit just 'it is a point' (b) The answer to this question requires good English in a sensible order with correct use of scientific terms. Quality of written communication should be considered in crediting points in the mark scheme maximum of 4 marks if ideas not well expressed any five from: clamp (steel) rod (horizontally) no marks if method quite unworkable hang plastic / sheet by rod through (one) hole hang plumb line from rod mark ends of plumb line on the sheet and use the ruler to draw a straight line Page 55 of 60

56 repeat with other hole centre of mass is where the lines cross check by balancing at this point maximum of 3 marks if no 'repeat with other hole' (c) (i) (turning) effect or moment force distance all three correct accept weight accept length 5 (ii) 7.6 allow 44 x 0.4 or 0.4 x 44 for mark 2 Nm or newton metre(s) do not accept N/m or N/cm 760 Ncm gains all 3 marks [0] 20 (a) (i) X at the centre of the lifebelt measuring from the centre of X, allow 2 mm tolerance in any direction (ii) any two from: if X is on vertical line below the hanger (but not at centre) can gain the first point only below the point of suspension accept (vertically) below Y at the centre (of the lifebelt) accept in the middle (because) the lifebelt / it is symmetrical or (because) the mass / weight is evenly distributed 2 Page 56 of 60

57 (b) Nm or newton metre(s) accept Newton metre(s) do not accept any ambiguity in the symbol ie NM, nm or nm 750 (moment) = force (perpendicular) distance (between line of action and pivot) or (moment) = gains mark 2 (c) Quality of written communication: for 2 of the underlined terms used in the correct context any three connected points from: low(er) centre of mass / gravity (more) stable or centre of mass / gravity will be close(r) to the wheels / axle / ground or less unstable less likely to fall over accept less likely to overturn do not accept will not fall over the turning effect / moment (of the weight of case) is less or so less effort is needed to hold the case ignore references to pulling the case so the pull on her arm is less 3 [0] 2 (a) Z weight or mass acts through pivot accept rod or base for pivot accept centre of gravity in line with pivot no (resultant) (turning) moment accept clockwise moment equals anticlockwise moment do not accept same weight on each side of rod Page 57 of 60

58 (b) (i) 30 N cm or 0.3 Nm allow mark for 2 5 or for full credit the unit must be consistent with the numerical answer do not accept joules 2 (ii).5 (N) allow mark for correct transformation allow 2 marks ecf their part (b)(i)/20 (ecf only if correct physics) 2 (c) 5 (cm) allow mark for 6.0 (cm) allow mark for a subtraction of from a value clearly obtained from the graph allow 2 marks for correct ecf using an incorrect value for (b)(i) 0.2cm allow mark for clearly showing correct use of graph using an incorrect value for (b)(ii) 2 [0] 22 any evidence of idea that weight acts through/near centre of mass/gravity/brick gains mark but clear indication that brick topples if vertical line through centre of mass is outside base line of brick or line of action of weight is outside base line of brick gains 2 marks [2] Page 58 of 60

59 23 gravity newtons balanced each for mark [3] 24 (a) evidence of or gains mark (credit 50/0 or 5 with mark) NOT 40/0 or 50/5 but 8 [N.B. negative not required] gains 2 marks units metres per second per second or (metres per second squared or m/s²) for mark (b) (i) idea that accelerates at first due to gravity air/wind resistance friction/resistance/drag with air increases with speed eventually gravity and friction cancel balance or (no net/accelerating force) [NOT terminal velocity] each for mark 3 3 (ii) idea a bigger resistance/friction/drag at any given speed (credit a bigger drag (factor)) for mark (c) evidence of 0 / 9.8 / 9.8 or 750/735(75) for mark [8] Page 59 of 60

60 25 (a) idea line of action of weight/force/gravity (if drawn: a vertical line through the centre of mass) falls outside the (wheel) base (mark NOT from diagram) for mark each 2 (b) ideas that less stable/topples more easily centre of mass at a higher level so need small angle to make line of action of weight fall outside (wheel) base for mark each 3 (c) idea that this is the most unstable condition (when bus used) or this makes c. of m. as high as it is likely to be for mark [6] Page 60 of 60